By using movement simulators it is possible to simulate movements in the real world, for example movements of a vehicle, aircraft or the like. By means of such movement simulators it is possible to give a driver of the vehicle the sensation that he is actually controlling the vehicle in the real world. For example, simulators from the prior art are known in which an image projection device, which displays to the driver an image of the external surroundings of the vehicle, is arranged in the field of vision of the driver. If the driver of the vehicle simulator then carries out control tasks such as, for example, accelerating, braking or making steering inputs, depending on the control input, the image of the surroundings which is displayed on the image projection device is correspondingly adapted to the control input and changed, with the result that the driver is given the sensation of actually moving the vehicle through the external surroundings of the vehicle.
In addition to fixed simulators in which the movement of the vehicle is simulated only by the displayed image of the exterior and the change therein, simulators are also known which in addition to this have a movement system which are configured to simulate the movements and accelerations which occur within the simulation in a defined movement space. In this context, up to 6 fundamental degrees of freedom can be modeled by the movement system within the movement space, depending on the type of simulator. In particular in the case of the simulation of aircraft, movement systems are used which permit the movement of the aircraft to be modeled in all 6 degrees of freedom (3 translational and 3 rotational degrees of freedom) within the movement space.
With a few exceptions, the movement systems which are driven hydraulically or electromechanically are constructed as parallel robots, which are, in turn, most frequently arranged as a hexapod or Stewart-Gough platform. The movement system generally has actuators which have variable lengths and which can move a platform arranged on the actuators with respect to a fixed reference plane by means of a corresponding change in length of the actuators. The actuators are, for this purpose, arranged in an articulated fashion both in the reference plane and on the platform, with the result that in the case of a change in length of the actuators and an associated movement of the platform, a change in angle between the reference plane and the actuator or between the actuator and the platform is also possible.
The movement values and/or acceleration values which are acquired in the simulation by the modeling of the vehicle are modeled in the movement space of the movement system. In this context, the high-frequency components of the translational accelerations and the high-frequency components of the rotational speeds are tracked directly in the corresponding degrees of freedom. The low-frequency components of the translational acceleration are, in contrast, displayed through the tipping of the movement platform, as a result of which the apparent weight vector in the simulator cab rotates. The other location displays, the external view or instruments, which are available to the user, continue to describe the original location, with the result that the impression of a prolonged, translational acceleration is produced.
According to the current prior art, the movement values and/or acceleration values which are acquired from the simulation are converted directly into forward kinetics of the platform by a change in length of the actuators which corresponds to open-loop control without feedback of the system state. However, for feedback, the system state of the movement system has to be determined with such precise detail and high quality that closed-loop control is made possible even with the various values to be simulated. For example, DE 10 2012 103 870 A1 describes a method with which the movement system state of a movement system can be detected in real time, with the result that basically closed-loop control becomes possible.
In addition to the current movement system state of the movement system, for closed-loop control it is also necessary to know which still available movement space, starting from the current movement system state, is in the movement system in order to be able to correspondingly simulate the movement values and/or acceleration values. This is basically because, owing to its mechanical design, the simulator can model corresponding movement values and/or acceleration values only within its mechanical limit, with the result that the “simulator” system is always limited to this mechanical system limit with respect to the values to be simulated.
However, a generally valid description of the working space of a parallel robot structure is not possible owing to the mathematically ambiguous solution of forward kinematics. Sunjoo K. Advani discloses in “The Kinematic Design of Flight Simulator Motion-Bases”, Phd dissertation TU Delft, 1998, an algorithm, which is valid for all degrees of freedom, for iteratively determining the system limits and the approximate description thereof by means of hyperboloids which is mathematically easy to define. In this context, the movable upper frame of the simulator is shifted virtually in one direction until the length, determined by means of inverse kinematics, of one of the six actuators infringes the mechanical system limits.
However, such an iterative, non-deterministic method for determining the system limits has the decisive disadvantage that it is basically not capable of real-time operation, since it cannot be predicted when the iterative, non-deterministic calculation method will arrive at a result. However, for basically real-time-capable closed-loop control of a simulator it is decisive that within the defined time increment for the closed-loop control the movement space limit which is required for the closed-loop control in this time increment is known, since otherwise real-time-capable closed-loop control of the simulator will no longer be possible. This cannot be provided by the iterative, non-deterministic method.